THE REACTION OF [RHH(PPH3)4] WITH THIOLS - A H-1 AND P-31 NMR-STUDY

In toluene or THF at -40°C [RhH(PPh3)4] reacts with RSH (R = Pri, Ph, CH2Ph) to give the unstable dihydro complex [RhH2(SR)(PPh3)3]. At 20°C decomposition of this complex with loss of H2 occurs via a five-coordinate species [RhH2(SR)(PPh3)2] to give [Rh(SR)(PPh3)3], which then dimerises to give the stable product [Rh2(μ-SR)2(PPh3)4]. In toluene/pyridine the initial product is [RhH2(SR)(PPh3)2(py)]. Loss of H2 gives [cis-Rh(SR)(PPh3)2(py)], which then undergoes further reaction with thiol. Where the formation of a five-coordinate dihydro species is prevented by the presence of a chelating ligand NArS- (NArS = 2-pyridylmethanethiolate, pyrimidine-2-thiolate, benzthiazole-2-thiolate and purine-6-thiolate) a thermally stable dihydrobis(triphenylphosphine)rhodium thiolate complex can be isolated. © 1990.